Methods and installations for ultrasonic peening are described in particular in French patents FR 2 815 280 and FR 2 815 281, using at least one sonotrode comprising a titanium body for putting shot into motion for inducing compression stresses in the treated part.
The following publications also relate to ultrasonic peening: U.S. Pat. Nos. 6,490,899 B2, 6,343,495 B1, 6,467,321 B2, 6,336,844 B1, 6,289,705 B1, 6,508,093 B2, US 2003/0115922 A1, U.S. Pat. Nos. 6,505,489 B2, and 6,536,109 B2.
The shot used and described in the past in those patents mainly comprises steel balls having a diameter of about 2 millimeters (mm) for example. The use of such shot does not enable treatment to be sufficiently intense on concave surfaces that present a radius of curvature smaller than that of the balls, or in the bottoms of certain setbacks.